Expandable styrene polymers are prepared on an industrial scale by the suspension polymerization of styrene in water. The bead polymer obtained after separation of the aqueous phase usually has a bead size of from 0.3 to 3 mm. In order to increase the yield, a decanter can be used to remove extremely fine polymer particles (.ltoreq. 0.3 mm), known as decanter material, from the suspension effluent. However, since these products have a total water content of from 1 to 10% by weight (surface water and internal water), the decanter material has hitherto exclusively been fed back into the preparation process as redissolver. The development of a saleable grade prepared therefrom has hitherto foundered on the work-up, in particular the drying, of such products since, even after removal of the surface moisture, internal water is released by the beads and results in unsatisfactory flow properties of the decanter material. As a consequence, agglomerates are formed, in particular on storage of the products, which makes conversion of the styrene polymers into foams considerably more difficult.